Implications for the UK of FPTP
FPTP is not proportional, so it is possible for a party to form a government despite gaining fewer votes than its opponent- this happened in February 1974, when Labour formed a minority government despite winning fewer votes than the Conservatives. FPTP also favours larger parties, due to the ‘winner-takes-all’ effect- large parties are more likely to have concentrations of support, enabling them to win more seats. People are less likely to vote for smaller parties as there is almost no chance of them winning (the ‘wasted vote’ idea), so may end up voting tactically to try to prevent another candidate winning- this is the idea of tactical voting. Therefore, Labour and the Conservatives tend to be over-represented in FPTP. Similarly, the SNP did extremely well in the 2015 election due to its concentrated support (despite the fact that they are much smaller than the two main parties). The Liberal Democrats have often suffered as a result of the lack of concentrated support- in 2010 the party won 23% of the vote, but only won 8% of seats available. In recent years, parties such as the Green Party and UKIP have also been disadvantaged- UKIP won 12.6% of the vote in 2015, but only 1 seat (0.2%).
Another implication of FPTP is that it tends to create a two-party system, due to the biases previously described. Only the Conservatives or Labour have a realistic chance of winning a majority of seats. Many seats are ‘safe seats’, where the concentration of support for one party is so great that there is no real possibility of any other party winning. Elections tend to, therefore, be fought over ‘marginal seats’ that change hands more frequently (around 100-150 seats, out of 650). Also due to this, FPTP is more likely to create single-party governments, with the 2010 coalition being the first for 70 years. Not only this, but the winning party can gain many seats on the basis of a small shift in support (the ‘winner’s bonus’ idea). For example, in 1997 Labour won a majority of 178, based on just 43% of the vote.
FPTP continues to be used because it suits the winning parties, who are therefore unlikely to want to give up this advantage by changing the voting system. The only reason a referendum was held on this issue in 2011 was the fact that the Liberal Democrats were in government, and the heavy defeat of AV put the issue of electoral reform to one side.
Implications of a MS & STV
The winner’s bonus, and bias towards large parties is reduced. In AMS, for example, if a party wins a large number of constituency seats (and is therefore over-represented), this can be ‘corrected’ through the distribution of the party list seats. This happened in the 2011 Scottish Parliament elections, where Labour had their representation corrected in such a way.
In addition, minor parties are more likely to win representation, so leading to multi-party systems. For example, the Green Party has had representation in the Scottish Parliament, Greater London Assembly and European Parliament, but until 2010 had no MPs in the House of Commons (and since 2010, have only had one). In 2014, UKIP won 24 seats in the European Parliament elections- the most of any party. The influence of the Lib Dems has increased in devolved assemblies, due to their traditional ‘third-party’ status.
These systems are also more likely to produce minority governments- that is, a party which may have a simple majority, but does not have an overall majority of seats. From 2007-2011, the SNP formed a minority government in the Scottish Parliament, as they were unwilling to enter into a formal coalition arrangement with another party. This, in turn, means that consensus politics is a likely outcome of proportional systems, as parties are aware that they are likely to have to work together in government. Coalitions are created through post-election discussions, which involve agreements on policy compromise. Frameworks for conducting the business of government between two (or more) parties also have to be set up).
AMS was chosen for Scottish and Welsh devolved governments because it was a compromise between having a broadly representative assembly (so satisfying smaller parties), but not being as radical as STV. Labour also reckoned that having AMS would ensure that it played a significant role in regional government.
STV was chosen for the Northern Ireland Assembly because of the importance of ensuring accurate, broad representation. Avoiding single-party domination was key, due to the part of the Good Friday Agreement which included a power-sharing provision between unionists and nationalists.